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Teresa Hansen, Section Editor
By John Bass, Xcel Energy and Guillermo Abreu, Emerson Process Management
When it comes to alarms associated with power plant operations, the adage “it is possible to have too much of a good thing” certainly rings true. The operators at Xcel Energy’s Pawnee Station would definitely agree.
Not too long ago, this 505-MW coal-fired generating station located in Brush, Colo., was commonly generating hundreds of alarms during an eight-hour shift. With roughly 39,000 possible alarm combinations, it was clear that something needed to be done to bring this alarming situation under control. That “something” is an ongoing, dedicated alarm management program supported by management and operators alike.
Pawnee Station’s experience mirrors what’s happening inside control rooms throughout the power industry. A proliferation of alarms is overwhelming operators, which can, in turn, affect the safety of plant personnel and the efficiency of plant operations. In fact, alarms have been determined to be the root cause of several abnormal situations during plant operations. So it’s no surprise that alarm management has become a hot topic among utilities.
At first glance, it seems logical that adding alarms would promote plant safety by quickly bringing potential issues to the attention of operators. This was not feasible when plants utilized hardwired controls, primarily due to the cost associated with wiring each alarm point. With today’s distributed control systems, however, it is possible to quickly and cost-effectively add alarms that previously would not have been practical.
It’s easy to see how alarms can quickly multiply. For example, alarm limits are often specified during control system design, but are rarely revisited for validity during actual plant operating conditions. Additionally, alarms tend to be constantly added but rarely deleted. In fact, the mindset “if it costs nothing, why not alarm it?” becomes an easy trap to fall into. The situation is often further exacerbated by inadequate operator training and poorly designed operator displays.
So while suppliers and power generators have understandably embraced alarm capabilities of control systems, if left unchecked and without a plant-wide alarm philosophy in place, the ease with which alarms can be added can become a double-edged sword.
How many alarms are too many? According to the Engineering Equipment and Materials Users Association (EEMUA), the average rate should not exceed six alarms an hour under normal conditions based on a 12-hour shift. During a transient condition or an engineered protection trip, the rate should not exceed 24 alarms per hour.
There are a number of other indicators, one or more of which should serve as a red flag that alarm management should become a priority. They include:
- Significant operating upsets generate an unmanageable number of alarms
- Minor operating upsets, as well as seemingly routine operations, generate a significant number of alarms
- Active alarms do not really require operator attention
- Some alarms remain active for significant periods of time
- When alarms activate, the operator is not sure of what to do about them, and
- When nothing is wrong active alarms occur.
Sounding the Alarm
Xcel Energy’s Pawnee Station began commercial operation in 1981 using a combination of Westinghouse 7300 combustion controls, a Control Data Corp. data acquisition system, a Westinghouse boiler interlock and interposing relay system and a Forney burner management system. From 1991 to 1994 Xcel Energy replaced these controls, including much of the balance of plant, with an Emerson WDPF system. Changes to environmental regulations and plant operating conditions required another upgrade to further improve plant performance and, consequently, the company implemented a program that migrated its existing WDPF equipment to Emerson’s Ovation expert control system.
Pawnee Station’s control system modernizations enhanced plant operations and provided greater insight into equipment and processes. The installation of advanced control technologies also expanded the plant’s ability to alarm equipment and processes. Operators would typically face 300 to 400 alarms during an eight-hour shift, which they would routinely acknowledge and silence. However, with so many alarms just determining which alarms required action and which were merely incidental was extremely difficult.
Long-time operators had institutional knowledge, accumulated from years of experience, which enabled them to better manage multiple alarms. For instance, an operator might understand that “when I start this pump I’ll get 12 alarms, but they don’t require any action.” However, this type of “on the job” knowledge is becoming more scarce - not just at Xcel Energy but throughout the power industry - as the Baby Boom generation retires and hands over the reins to less-experienced personnel.
Xcel Energy understood the importance of effectively utilizing alarms to help assure plant reliability and therefore approached the situation proactively. Several people who championed the cause made the case to management, who agreed to launch an alarm management initiative.
Based on real-world experiences designing, implementing, operating and maintaining an alarm management program at the Pawnee Station, the alarm management team, in conjunction with Emerson, developed a set of best practices that can be adopted across Xcel Energy’s fleet of plants and also serve as a model for other utilities seeking to better manage alarms. According to these best practices, several key components are required for the development and ongoing implementation of a successful alarm management program. These components are:
Philosophy
Philosophy, according to Xcel Energy, is where it all begins. The alarm management philosophy is a defined strategy of what will alarm; how alarms will be annunciated, viewed, acknowledged and recorded; and ensuring that alarms are cleared either operationally or through the maintenance system. The philosophy is the roadmap for effectively implementing a successful alarm management program.
Determine Alarm Regions and Priorities
As a next step, Xcel divided the plant into regions then reviewed and assigned each point to a specific region based on areas of the plant, processes or operator responsibility. For example, at Pawnee Station, operators control the boiler system, feedwater system, condensate system, air system and fuel system in the main control room. They control the water treatment facility from a separate control room. Operators control the ash systems from a third control room and the coal handling systems from a fourth. At each control location, operators should annunciate and acknowledge only the alarms pertaining to those systems. After determining the regions, operators should define priority schemes by reviewing and assigning the proper significance to each alarm point.
Dead-band Management
Dead-band management is the proper adjustment of resets for both analog and discrete alarms, as well as proper configuration of incremental alarms. Alarm dead-bands must not allow the point to continually alarm, or “chatter,” on normal process variations. For example, if a drum-level-low alarm occurs at minus 10 inches and the normal drum level “swing” is plus or minus one inch, then the dead-band would need to be greater than one inch.
 Pawnee Station’s control system generated hundreds of alarms during an eight-hour shift; there were 39,000 possible alarm configurations. Photo courtesy Xcel Energy. |
Another variation used by Xcel Energy is time delays on alarms such as an oil temperature alarm on the pulverizer oil system. At Pawnee Station, oil temperature is maintained through cooling water controlled in an on/off control configuration: the cooling water valve opens at 100 F and the high alarm activates at 105 F. Because the cooling process takes about five minutes, the temperature sometimes reaches 105 F before it decreases. In this scenario, a short-time delay on the alarm prevents unnecessary annunciation.
Tackling alarm dead-bands can significantly reduce alarms. At Pawnee Station, dead-band management resulted in considerable improvements - enough, in fact, to get buy-in from some operators who were skeptical about the tangible impact an alarm management program would have. Consequently, these operators have become part of the continuous improvement process for maintaining the alarm management program.
Alarm Rationalization - Suppression and Delays
Alarm rationalizationuses logic to prevent alarms for equipment that is not in operation. For example, if an operator stops a boiler feed pump, all alarms that could occur and that are associated with this operator action should be suppressed. These might include:
- Boiler feed pump stopped
- Boiler feed pump discharge valve closed
- Boiler feed pump suction valve closed
- Boiler feed pump vibration alarm
- Boiler feed pump bearing temperature alarmM
Alarm suppression is also useful for certain routine events. For example, if each day the continuous emissions monitoring (CEM) system automatically calibrates, alarms associated with the CEM system should be suppressed when the “in calibration” signal is present.
Operator Training
The experience at Pawnee Station demonstrated that for an alarm management initiative to be beneficial day in and day out, plant operators must understand the functions of each of the other key alarm management components: philosophy, dead-band management, alarm rationalization and more. What’s more, operating procedures must be closely aligned with the alarm management program. This is accomplished through training that addresses the philosophy, the system’s use and alarm response. To ensure operators are fully engaged, obtaining feedback throughout the alarm management program is an important aspect that should not be overlooked.
 To ensure operators are fully engaged in an alarm management program, they must understand the importance in obtaining feedback from the alarms. Photo courtesy Xcel Energy. |
Power generators planning to implement an alarm management program should also use another valuable resource: the expertise of their control system supplier. For example, in addition to its work with Xcel Energy to define best practices, Emerson is rolling out a broad set of alarm management initiatives for customers who use its Ovation system. The tools - which allow plant personnel to analyze alarms, define and configure alarm strategies and further simplify alarm resolution - are designed specifically for its Ovation expert control system and are intended to be utilized as part of a utility’s overall alarm management program.
Bottom Line: Don’t Be Alarmed
So how do power plant personnel know if the alarm management program is working? A low alarm number is the best indicator of a good program. Today, Pawnee Station typically reports less than one alarm per hour or eight alarms per shift during normal operation - a dramatic drop from the hundred alarms it previously experienced and well below EEMUA guidelines. Moreover, the plant typically experiences fewer than 20 alarms per trip.
Of course, these results did not happen overnight. A core team worked as many as 10 hours a week for approximately two years to thoroughly address each component. To ensure continued success, Xcel Energy treats alarm management as a continuous improvement process. For that reason, a member of the core implementation team spends an average of one or two hours a month reviewing alarms. The improvements have not gone unrecognized. The core alarm management team is sharing its expertise and lessons learned with other Xcel Energy power plants so that they, too, may benefit from the experiences at Pawnee Station.
While enhancing safety is a key benefit of an effective alarm management strategy, other important advantages exist, as well. Alarm management plays a role in reducing operator fatigue and stress, thereby contributing to increased productivity and job satisfaction. At Pawnee Station, for example, time spent by operators to respond to and silence numerous alarms can be applied toward other activities.
It’s also important to note that operators are more confident. When an alarm does sound, they know something needs to be addressed and they can focus on the appropriate course of action.
Although alarm reductions don’t show up on the balance sheet, per se, Xcel Energy realizes that a plant trip or equipment damage caused by the inability to appropriately respond to excessive alarms can have a real, negative economic impact. So from a financial perspective, by helping plants achieve higher levels of availability and reliability, an effective alarm management strategy does indeed contribute to bottom-line profitability.
Alarm management can be a vital component of a comprehensive strategy for achieving operational and financial improvement. Implementing an alarm management program can be a daunting challenge. However, instead of wondering, “Can we afford to dedicate the necessary resources toward this effort?” perhaps the better question for power generators to consider is, “Can we afford not to?”
PRB Coal Safety Design Considerations for New Greenfield Plants: An EPCC’s Perspective
James H. Brown, P.E., Fluor Power
Many coal-fired power plants have converted from bituminous coals to Powder River Basin (PRB) coals in the last decade to take advantage of PRB coals’ low sulfur content and environmentally friendly characteristics. While PRB coals burn cleaner than other coal types, they also create some unique safety issues. The highly friable coals can become fragmented and form coal dust that is highly volatile and can easily self-ignite. The PRB Users Group is raising awareness about PRB coals’ safety issues; however, most of the related information concentrates on specific design features that can be incorporated into existing plants that are switching fuels.
Currently there are nearly 150 new coal-fired plants being developed and constructed in the United States. Many of these plants are or will be located on greenfield sites and will burn PRB coals, making it important to address PRB safety issues for new power plants. This article reviews the design and safety aspects that should be considered in a new greenfield, PRB coal-fired power plant, such as the power generation facility Fluor is designing, building and commissioning for Newmont Mining in northern Nevada. The 200 MW TS Power Plant (TSPP) presented the Fluor design team with some unique challenges when trying to ensure the plant can be operated safely with this potentially explosive fuel.
While the plant operations team and its operating, maintenance and housekeeping procedures and practices will bear much of the eventual responsibility for ensuring plant safety; the plant systems’ designers are responsible for ensuring plant operators can operate the plant safely without undue additional effort and staffing. Safety must be a design consideration from the coal unloading station to the transport conveyors and from the coal storage yard to the silos through the feed train system up to the burners. Additionally, safety design features within the buildings that house this equipment must be considered.
Coal Handling, Unloading and Conveyance
Addressing the issue of dust control directly at TSPP included attacking the root of the problem - dust creation. Obviously, limiting the dust that is created will reduce the amount that must be suppressed or removed through plant housekeeping procedures. Developing “engineered” coal flow transfers along the conveying path can greatly minimize the dust that’s created. The goal of directional flow-type transfers is to keep the coal in contact with chutework as the coal changes direction. Most coal handling system designers and system subcontractors are aware of the PRB coal-related issues and benefits of eliminating dust; therefore they have incorporated design features such as totally enclosed chuteworks, “spoon drops” to reduce impact turbulence, and overflow hoods.
 Extended skirtboards and tight clearances between the wear plates and the belts are perhaps the most important conveying features for a PRB coal-fired plant. |
Extended skirtboards and tight clearances between the wear plates and the belts are perhaps the most important conveying features for a PRB coal-fired plant. Designers should closely consider these features and operators should closely monitor them for coal spillage containment during operations. Designers also should include chutework access doors with good fits and adequate seals. Proper installation and alignment of these design features is critical. Roberts and Schaefer provided the coal conveying system at Newmont’s TSPP. The company’s approach to minimizing dust creation included these design features, as well as dust suppression systems designed to contain dust at the unloading building and reclaim areas. The dust suppressions systems utilize a surfactant that ensures proper distribution of the spray water among the coal particles.
Coal Storage Yard
PRB coal-fired plant design must consider even the coal pile. Fluor, along with input from Newmont’s plant operator, DTE Energy, designed the active and long-term coal storage yards. (The plant has a 30-day coal storage pile.) The coal pile dead storage was designed to the requirements of DTE’s material handling operators with regard to angle of coal pile for rolling stock operations and proper compaction. DTE required a 2-to-1 side slope for the dead storage pile. The coal pile includes an HDPE liner with a native soil sand bed over-liner for protection. The pile is designed for stockout into 18-inch lifts. The coal pile lifts result in high compaction, achieving greater than 75 lb/ft3 density to ensure oxygen deprivation. The coal pile includes dust suppression monitor hydrants in the storage yard that are separate from the fire protection monitor hydrants. These dust suppression monitor hydrants are used by the material handling operations group during compaction and coal pile management to minimize dust and assist in compaction. A heavy equipment washdown area is also included to ensure dust and particles do not build up on the vehicles and create potential hazards.
Building Systems Protection
Once the coal is reclaimed from the coal pile and is crushed, it has even more fines that further increase the potential for dust creation. To minimize dust collection on horizontal surfaces, Fluor designed the coal silo filling bay at TSPP as a separate enclosed room that includes wall and ceiling architectural panels to cover the structural steel support beams, girts and roof support steel. The room’s wall panels and concrete floor are painted a light color so operators can clearly see if a significant dust layer builds up on these surfaces. The concrete curbed floor includes a floor drain system that discharges to the plant’s air preheater wash sump, which has a decanting separation chamber to settle coal fines before they are pumped to the facility’s evaporation pond. High pressure washdown water is provided at this boiler building elevation. Additionally, a vacuum cleaning tubular distribution system is provided at the coal silo filling bay, feeder floor and pulverizer area that can be used to dry convey coal spills or dust to grade for disposal. Lighting in this area and throughout the enclosed structure plays an important role in ensuring operations maintain clean areas. At TSPP, a separate electrical room contains the power supply and distribution equipment; this is another feature designed to minimize the risk of fire ignition. All electrical equipment in the room is designed for the appropriate Electrical Hazardous Classification in accordance with NEC Article 500-2.
A reversing conveyor is used to distribute the coal among the facility’s three coal silos. The belt includes a dust collection feature that discharges dust back into the silos via a baghouse located on top of the boiler building. The ventilation equipment for this coal silo filling bay room is generously sized with multiple air changes to accommodate coal delivery and ensure combustible gas levels in the room are controlled to safe levels.
Coal Silo Design
Typically, as long as the coal in the silos is in transit, the coal storage vessels remain fairly safe; however, if bridging or rat-holing occur and coal is allowed to remain stagnant, there is a serious combustion potential. At TSPP, the benefits of a coal flow study were incorporated into the coal silos’ design. This design ensures mass flow through the silos to the feeders. Plant operations’ practices include switching between silos periodically to ensure the silos do not sit stagnant for long periods. Should an emergency maintenance situation prevent the silo from being emptied prior to an extended outage, the coal silo may be emptied via an emergency discharge connection on the gravimetric feeder. A transition piece transports the coal to the emergency dump chutework that is routed outside for truck loading. This feature allows operators to remove coal if an extended outage is anticipated.
Each coal silo will also include a CO monitor which will be used to alert operators of a potential fire within the silos. Experience indicates that CO monitors can indicate when a potential issue exists before temperature monitors can. The coal silos also include top and mid-height connections for fire-piercing rod injection should a silo fire start.
The fire protection and detection systems designs for the coal handling system at TSPP were not significantly different than those systems supplied for any other types of coal-fired plants, with the exception of a F-500 fire suppressant used for coal silo fire protection. This product uses encapsulator technology and, when used in combination with the fire piercing rods, can attack directly at the seat of any coal silo fire.
The final design approach for projects using PRB coal has to be a collaboration of efforts from the owner, engineering, procurement and construction contractor (EPCC) design firm, owner’s engineer, owner’s operations and maintenance team and coal handling equipment supplier. When designing Newmont’s TSPP project, the Fluor design team took a whole project approach to safety, which included following the coal supply from the point of arrival on-site to combustion in the boiler. The design also considered the potential maintenance and housekeeping burden that may be placed on the plant operations team.
Newmont and other plant owners have found that coal from the Powder River Basin comes with many inherent advantages including its environmentally friendly low sulfur content and the coal source’s proximity to many coal facilities being planned in the near future in the western United States; however, it is clear that its use also imposes specific additional risks associated with its combustive nature. Coal plant designers, owners and operators must learn from the lessons of the past decade of coal fuel switching to PRB, but must also take a holistic view to ensure the coal handling system provides adequate safety measures to mitigate these risks.
Heat Activated Epoxy-based Materials Help Enhance Steam Pipe Repair
Years of environmental attack have caused power plant water and steam pipes to corrode and degrade. As maintenance personnel struggle to repair these damaged lines, scientists aim to develop repair materials that will efficiently accomplish the task. A key component of successful leaking and corroded pipe repair work is the ability to perform in situ applications. Many piping systems were not designed and constructed so that portions of the lines can be shut down without interrupting plant operations.
The need for emergency repair materials has increased as piping systems age and degrade each year. In addition to providing rapid repair solutions, the repair products must be easy to apply and tolerant to surface contamination commonly found in water and steam piping.
Over the last few years, Belzona technical consultants have performed several successful repairs on in-service pipes with temperatures up to 302 F. From plugging active steam leaks to protecting hot pipes against corrosion under insulation, the heat activated materials used in the repairs are suitable for a variety of fast and effective in situ applications.
Chemists have successfully formulated two single-component heat-activated epoxy-based materials; one in paste form and the other in a less viscous coating. These materials require no mixing or measuring and can be applied using a mastic gun, spatula or paint brush (Photo 1). Cure does not commence until the material’s temperature is above 158 F, therefore the usable life is effectively unlimited at room temperature.
 Photo 1. Belzona 1251 (heat activated-metal) is being applied via metal spatula. Note the thick gloves the applicator has donned for protection against the heat. |
When active steam leaks were found at a power plant, Belzona was contacted to perform the repair (Photo 2). The plant’s maintenance manager was unable to shut down the system and informed the Belzona technical consultant that an attempt to repair the leak with welding techniques was unsuccessful. He also said the pipes were badly corroded and located in a confined space.
 Photo 2. The application area is secured with yellow ‘CAUTION’ tape. Steam can be seen emanating from the pipes. |
The technical consultant measured the pipe’s temperature with an infrared thermometer, which indicated that the steel surface temperature was about 200 F. Once the pipes were prepared by hand wire-brushing, a layer of Belzona 1251 (heat activated-metal) was applied. Then an aluminum sleeve was also covered with the heat activated material and tightened with a clamp (Photos 3 and 4). Once the material cured, the entire area was coated with Belzona 5851 (heat activated-barrier) to further protect the piping from corrosion and environmental attack. When the clamps were removed, no steam was seen. In addition to being leak free, the pipes are now also protected from further corrosion.
 Photo 3. Belzona 1251 (heat activated-metal) is laid out prior to the application. |
The materials show exceptional adhesion to oily and unprepared metals, as long as rust or mill scale is removed. Tensile shear adhesion values at elevated temperatures (212 F) on clean, ground steel are 2800 psi for the coating material and 2200 psi for the paste grade. On a steel surface prepared according to ISO 8501-1 St 3 (manually abraded), tensile shear adhesion values decrease only slightly to 2600 psi and 2100 psi for the coating and paste grades, respectively. In extremely limiting conditions, where preparation can only be done via wire brush (ISO 8501-1 St 2), 1700 psi for the coating and 1200 psi for the paste material can still be accomplished. In addition to excellent adhesion, these materials also exhibit excellent resistance when immersed in various chemicals and also show no visible signs of corrosion after 1,000 hours of salt spray according to ASTM B117.
The heat-activated materials used in this example can be used to coat, repair, bond and protect a variety of metallic substrates where typical maintenance materials would degrade at the high working temperatures found in these applications.
High Resolution Bolt is a Smart Fit for Power Plant Applications
Critical bolted connections often require exacting tightening procedures to reach the optimum clamp load. While tightening by torque wrenching methods is quick and easy, a given torque can produce tensions or clamp forces varying by as much as 5-to-1, depending on bolt plating, lubrication, thread condition, nut and washer material and 71 other variables, according to a U.S. Air Force study.
To remove this uncertainty, Stress Indicators Inc. developed Direct Tension Indicator (DTI) SmartBolts that respond only to bolt tension and not to torque. DTI SmartBolts, which have been available for more than 20 years, were invented to set up the proper bolt tension with no need for torque wrenches, strain gages, wires, electronic or ultrasonic equipment. Plant maintenance personnel are not required to touch or contact the fastener at all to verify its clamp load condition. A quick visual inspection is sufficient because the degree of tension can be estimated by observing the color of an indicator located on the center of the bolt’s head.
The indication is bright red when loose, and gradually darkens to a deep black as the bolt is tightened. A loose fastener is obvious even at a distance or, in some cases, in moving machinery. The standard tension accuracy is specified to be ±10 percent.
These bolts have been installed in many power plants during the past two decades and many are still in use. The Electric Power Research Institute (EPRI) analyzed the use of SmartBolts in power plants. In its report, EPRI concluded that the bolts should be considered a cost-effective way to reduce nuclear power plant personnel’s radiation exposure. SmartBolts have survived intensive radiation exposure tests, and will soon be installed in nuclear plants for further evaluation.
While the SmartBolts have been beneficial in many power plant scenarios, they do have limitations, the main one being that the indicator’s color-change scheme is not designed to show an over-tension condition. Once design tension is achieved, the indicator remains black if it is tightened further, thus giving no indication of over-tension. Another limitation is that the color change associated with a loss of, for example, 10 percent of tension may be difficult to resolve in real world conditions.
Realizing that these limitations needed to be eliminated, Stress Indicators developed a new high-resolution (HR) SmartBolt. The HR SmartBolt is a significant upgrade of the flagship DTI SmartBolt; it is more accurate and easier to read. The HR SmartBolt contains a sensitive optical micro-indicator element that allows quick-look inspection. The indicator remains yellow as the fastener elongates while being initially tightened. When about 85 percent of the design tension has been achieved, the indicator rapidly begins to change colors and turns bright green at 100 percent tension. When tightened beyond design specifications, the indicator darkens until it is nearly black. In addition, should the bolt loosen more than 10 percent to 15 percent, the indicator returns to bright yellow, indicating a problem.
The color-coded system works well for critical inspections and inspections in high-radiation areas or areas where the bolts are hard to access. Once a bolt is installed, the proper tension may be verified without contact with or loosening of the fasteners. It also means that loosened fasteners in critical situations may be easily identified and corrected, thereby averting catastrophic incidents.
The HR SmartBolt indicates bolt tension through direct measurement of bolt elongation. Accuracy is improved over the DTI SmartBolt because each bolt is calibrated at design tension during assembly. The HR indicator is sensitive to an elongation of 60 millionths of an inch, which corresponds to a tension precision of around 2 percent when installed in high-strength bolts. If the indicator is “grass green,” the bolt is doing its job.
Torque wrenches respond to only the applied torque, which is only weakly related to tension. A large part of this torque, as much as 80 percent to 90 percent, is required to overcome friction, which can vary significantly in different situations. The result is that a perfectly accurate torque wrench may produce errors in bolt tension as much as 25 percent to 50 percent according to many engineering studies
In contrast to torque wrenching, SmartBolt’s clamp load is independent of friction and remains reliable and reproducible through countless cycles of tightening and loosening. The process is completely reversible and there are no moving parts to wear out. Twenty-year-old DTI SmartBolts still operate as reliably as when they were new. A life expectancy exceeding 20 years is similarly forecast for the HR bolts, since they use the same inert materials and components. Although the HR SmartBolt is a significant upgrade from the DTI SmartBolt, the original DTI SmartBolts are still appropriate for less demanding applications.
GE Busway, the Electrical Distribution division of General Electric, has used DTI SmartBolts in its Spectra Series Busway systems since 1997. The fasteners are used to join modular electrical conductors that supply power throughout its plants. The bolts make inspection of these high-voltage busway joints high in the plant’s overhead easier and safer and provide visual joint integrity assurance.
